Ion Beam Scan Control for Dose Uniformity
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Solution Overview
Problem
Ion beam irradiation systems face inefficiencies in beam irradiation due to non-uniform dose distribution and increased ion beam usage outside the wafer, especially when using reciprocating wafer moving functions, leading to reduced productivity and energy inefficiency.
Innovation Solution
The system employs a beam scan control calculation unit that adjusts beam scan speed and width dynamically, using scan voltage correction functions to create multistage scan areas matching the wafer's shape, ensuring uniform dose distribution and reducing unnecessary ion beam usage by adjusting mechanical Y-scan speeds based on real-time beam current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the beam scan width is kept constant in all Y-direction regions, then the beam scan control is simple, but the useless ion beam irradiation to outside of the wafer increases at both Y-direction edges, reducing beam irradiation efficiency
Solution Approach 1:
The beam scan width is made dynamic by changing it according to the Y-direction position. Specifically, the beam scan width is reduced in the Y-direction edge regions compared to the center region, allowing the beam scan area to match the wafer shape and reduce useless irradiation while maintaining relatively simple control through predetermined correction values.
2Productivity
If the beam scan width is reduced to match the wafer shape, then the beam irradiation efficiency is improved, but the in-plane dose uniformity becomes difficult to maintain
Solution Approach 1:
Different beam scan widths are applied to different Y-direction regions of the wafer. The beam scan width is set to be larger in the center region and smaller in the edge regions, creating local variations in scan parameters that match the wafer geometry while maintaining dose uniformity through predetermined correction values for each region.
Solution Approach 2:
The beam scan width parameter is changed according to the Y-direction position. By predetermining correction values for different Y-position ranges, the system adjusts the beam scan width parameter to match the wafer shape, improving irradiation efficiency while maintaining dose uniformity through controlled parameter variation.
3Device complexity
If the ion beam current fluctuates during irradiation, then the irradiation process is simple without real-time adjustment, but the in-plane dose uniformity is compromised
Solution Approach 1:
A beam current measurement device measures the ion beam current during irradiation, and a control device adjusts the beam scan width based on the measured current to maintain constant dose amount. This feedback mechanism compensates for current fluctuations and maintains dose uniformity without requiring complex real-time parameter adjustments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances productivity by reducing ion beam irradiation time and energy consumption while maintaining in-plane dose uniformity, minimizing useless ion beam irradiation and sputtering contamination.
Implementation Method 1
a beam deflection scanner, which scans the ion beam in a horizontal direction
Implementation Method 2
implant ions to a circular wafer for semi-conductor device
Data Source
AI summary
An ion beam irradiation method comprises calculating a scan voltage correction function with the maximum beam scan width depending on the measurement result of a beam current measurement device, calculating each of more than one scan voltage correction functions corresponding to each of scheduled beam scan widths depending on the calculated scan voltage correction functions while satisfying dose uniformity in the horizontal direction, measuring a mechanical Y-scan position during the ion implantation, changing the scan voltage correction function as a function of the measured mechanical Y-scan position so that the beam scan area becomes a D-shaped multistage beam scan area corresponding to an outer periphery of a half of the wafer to thereby reduce the beam scan width, and changing a mechanical Y-scan speed depending on the change of the measurement result of a side cup current measurement device to thereby keep the dose uniformity in the vertical direction.